A known fixing device for use in an image forming apparatus is configured to heat a film with a nip plate contacting an inner peripheral surface of the film.
The fixing device includes a first film guide configured to guide the rotation of the film at each end of the nip plate, a second film guide having a generally semicircular shape and configured to guide the rotation of an end of the film, and a restricting member disposed at a position corresponding to the second film guide and configured to restrict the movement of the film to its longitudinal direction.